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Re: carry **arguments through different scopes/functions

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On Sun, Jan 31, 2016 at 7:19 AM, <c.buhtz@posteo.jp> wrote:

> I am not sure what the problem is here, so I don't really know how I
> should call the subject for that question. Please offer a better
> subject.
>
> The code below is a extrem simplified example of the original one. But
> it reproduce the problem very nice. Please focus on the variable
> `return_code`.
>
> There is a `list()` of numbers without the number `7` in. The code
> check if the number `7` is in and should tell that it is not in. But it
> does tell me that `7 is in`. ;)
>
> I think I didn't know some special things about scopes of variables in
> Python. This might be a very good problem to learn more about that. But
> I don't know on which Python topic I should focus here to find a
> solution for my own.
>
>     #!/usr/bin/env python3
>     import sys
>
>     def walkOn_ids(ids, handlerFunction, **handlerArgs):
>         for one_id in ids:
>             handlerFunction(one_id=one_id, **handlerArgs)
>             print('after handler-call for id {}\t{}'
>                   .format(one_id, handlerArgs))
>

>     def _on_id(one_id, return_code):
>         if return_code is False:
>             return
>

The above returns None, not False.  Maybe you want False, so return False.
However, when you call this function below, you set return_code = True, so
it will never be False

>
>         if one_id == 7:
>             return_code = True
>         else:
>             return_code = False
>

The above could be just:
           return one_id == 7

no need for if/else

>
>         print('one_id: {}\treturn_code: {}'.format(one_id, return_code))
>
>
>     def _isSevenInIt(ids):
>         return_code = True
>
>         walkOn_ids(ids=ids,
>                    handlerFunction=_on_id,
>                    return_code=return_code)
>
>         return return_code
>

This will always return True because you set return_code = True and never
change it.  You might want this:

          return_code = walkOn_ids(...

>
>
>     ids = [1,2,3,4,5,6,8,9]  # NO 7
>     print(ids)
>
>     if _isSevenInIt(ids) is True:
>         print('7 is in')
>     else:
>         print('no 7 in it')
>
>     sys.exit()
>
> Of course I could make `return_code` a `global` variable. But that is
> not the goal. The goal is to carry this variable inside the
> walker-function and bring the result back. In the original code I will
> use some more complexe data structures with `**handlerArgs`.
>

Before you start randomly making variables global, make sure you have
written code that does what you want it to.  Globals to fix bad coding will
quickly bring a big mess.  Of course its more subtle than this, but mostly
globals are a very bad idea.

> --
> https://mail.python.org/mailman/listinfo/python-list
>



-- 
Joel Goldstick
http://joelgoldstick.com/stats/birthdays

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Re: carry **arguments through different scopes/functions Joel Goldstick <joel.goldstick@gmail.com> - 2016-01-31 08:12 -0500

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